Experimental Study On Low Turbidity Water By Enhanced Coagulation Of Recycling Sludge

China’s water resources is abundant, but the per capita output is only1/4of theworld average level. In recent years, with the proportion of lakes and reservoirsincreasing, the existing water treatment process of water plant is difficult to obtaingood effect of water purification because the characteristics of lakes and reservoirs havethese aspects: low turbidity, stable quality and micro-polluted water. Coupled with thenew national standard for water quality requirements improving, the water plants haveto adopt different methods to enhance coagulation, such as enhanced coagulation,flotation, micro-flocculation filtration and other methods of processing for low turbidity.In the background of drinking water resource shortage, water treatment plant graduallybegan to regard wastewater as a resource for recycling. It provides a new approachfeasible for reducing water consumption in the period of low turbidity. Beside reducingwater consumption, production from wastewater reuse can have a great water-savingsignificance and economic value. But there are certain risks when the production ofwastewater reusing. Because the production of wastewater reuse may lead to higherwater content of heavy metals and some organics. All of them will inevitably bringsome risks for the conventional treatment process.Firstly, through the jar test to verify the performance of different wastewater andsludge sedimentation activity. The reflux test was done on the basis of the tank sludgewater, filter backwash water and a mixture of both water. The mixture of water turbidityis regarded as a control factor to coagulation tests. Comparing three groups of trials todetermine the optimal mix of water turbidity range. Based on the jar test, theconstruction of a continuous pilot test device was set up in order to accurately reflect thedifferent production wastewater reuse. There are certain risks when the production ofwastewater reusing because the production of wastewater reuse may lead to higherwater content of heavy metals and some organics. The sludge reuse security is evaluatedseparately from the indicators of conventional, organic and metal. Establishing acombination system of genetic toxicology to detect drinking water mutagenicity.The jar test results showed that: reusing tank sludge water, filter backwash waterand a mixture of both water refluxt will discover that reusing the wastewater couldenhance coagulation、save the dosage.At the same dosage, the water of mixed effluentis the best, followed by sludge water，backwash water is worse compared with theprevious two types of water on both sides; There exists the best conditions for recyclingin all of them and have a good saving dosage effect within this interval range. The bestmixed water turbidity of the sludge and mixture of the two water is in the range between 20~80NTU, scope and backwash water is only30~50NTU; Based on water productionand waste water ratio, it is recommended the mixed water turbidity as a control variable.Adjust the sludge water regulation on the basis of refluxing the backwash wastewater inratio of100%in order to enhance coagulation.Continuity test results found that at the same dosage, reusing proper conduct ofsludge could have good turbidity and color removal. The difference between TOC andDOC dose not produce big change. The aluminum, iron, manganese difference showedthat reusing sludge may enhance the removal of aluminum. The removal of iron is notobvious, but there is no enrichment. But reusing sludge dose not have an effectiveremoval on manganese.Toxicity of wastewater comes back to a four-stage detection method using geneticresearch literature. Selecting luminescent bacteria as the first stage of the acute testmethods; The second phase depends on the genetic point SCGE test, TK gene mutationassay, micronucleus test as the detection DNA, genes and chromosomes test methodsrespectively; Phase III trials uses the UDS test and terato sperm test to detect the geneticmutation of germ cell; Selecting specific-locus test and heritable translocation test as thestandard test in phase IV.